Software Discussion
The software is what makes this product useful. Without software it would have no value. Luckily the guys at DSP4you are both very responsive and very interested in putting out software that is not only versatile, but they will also listen to feedback and add functionality.
Software is available in the form of MiniDSP plugins, each costing $10 and with free updates. A miniDSP can only have a single plugin at a time, but these individual plugins can do a lot at the same time. The plugin I purchased was the Stereo 2 Way Advanced. This will take two inputs and have two respective outputs for each. The reason I chose the advanced plugin was for BiQuad filters. These are mathematical filters which allow a lot more functionality than the basic "butter worth, bessel, linkwitz-riley" options which the miniDSP offers. The advanced plugin still allows access to those simple filters but gives you a world more of "things you can do". I'm talking cascading to a point of a 96db/octave filter, or very intricate parametric notching, or working below the miniDSP's "technical" passband. Whereas the basic filters will limit you to 20hz, you can go as low as you want with biquad filters - so if you just built a DIY ported sub and want a 13hz high pass filter, this will do it for you!
My first order of action was to implement a slight linkwitz transform to boost lower frequencies on a sealed subwoofer, as well as a high pass filter to limit excursion at high power levels which my pro amp is capable of. In order to do this you must model the transfer function of the filter and convert that to biquad formula values. Google "BIQuad MiniDSP" for information on how to do this in a demo version of LSPCad if you're interested.
A few possible uses of the Stereo 2-way crossover include
-Crossing a pair of amplified speakers to a single sub at your desired frequency and slope
-Crossing a pair of amplified speakers to a pair of subs in the same manner
-Making a 2-way active loudspeaker
-Inputting a mono subwoofer signal into both inputs and outputting four separate, EQed, phase aligned subwoofer signals for integrating multiple subs
-Inputting a stereo sub signal and doing likewise with two subs per input.
-simple parametric EQ
Other available plugins include a 4-way advanced crossover (which will require two MiniDSP units for a pair of speakers), Graphic EQ, non-advanced plugins, and a mixer.
One last usage worth noting for the miniDSP is excellent compatibility with the Room Equalization Wizard program. Think of this combination as being a sort of Auto-EQ. By doing major equalization on this unit, you can leave other equalization to your receiver's EQ. This can be done simply by importing an REW measurement file. Doing this will require a measurement mic, mic stand, and USB mic preamp.
Currently, the miniDSP software's not compltely flawless, as with most software you're of course going to run into a glitch here and there. I had a sync error on my first attempt at syncing the DSP to the computer... basically it took like 20 minutes to sync and nothing was happening. If you come across this issue, simply Alt+F4 out of the program. Yes, it's scary because the program tells you NOT TO DO ANYTHING. When I reopened the program nothing went wrong and it synced in about 5 seconds and everything worked fine.
I also made a mistake to sync with a few default settings in place. What I ended up with was the miniDSP treating my subwoofer as a tweeter high passed at 1khz. Needless to say, i spent the next hour trying to figure out what was wrong and why I was getting no sound! Can you imagine a subwoofer designed to filter out frequencies below 1000hz? Before syncing, check every stage of the theoretical crossover, even if it's not a stage you're using right now.
Listening Tests
A) It sounds a bit like a banana cake. Very soft with a thick texture and a certain familiar grain being used. THe low end shines with a hint of vanilla and the highes sparkle like a good glass of bubbly. The midrange came across as flat however, somewhat breezy though I might add.
B)I ain't listenin to no DSP dude. All you need to know is:
28/56bit DSP Engine
24 bit ADC/DAC resolution
48kHz sampling rate
Conclusion.
If you're a DIYer with an interest in building your own speaker, forget about going passive. Active will give you the kind of options, flexibility, and yes, simplicity, that passive just can't. With the miniDSP, it's not only affordable to at least bi-amp, but also accessible. A pair of miniDSPs will let you design your own 4-way loudspeaker pair. If you've got a computer setup, this can make hooking up an external subwoofer to a pair of active monitors a lot simpler than having a giant receiver on the desk. If you just need a parametric equalizer, this is that too. It's many things, and that's exactly what makes it a worthwhile purchase for many people. I definitely recommend buying one if you've got electronic limitations. The setup might not be plug and play, but once you've got it up and running, it'll have been a worthwhile venture. Did I mention it's tiny?
